In the winter of 2007, John Maloof, a 26-year-old Chicago realtor, stumbled upon a box of negatives at an auction house. He paid $400, hoping it might hold some vintage photos of his neighborhood. He stuffed the box in a closet. There the images sat for a couple of months, until he had time to scan a few into his computer. "Little by little I realized how good they were," he told me. In the end, he collected more than 100,000 negatives, including a few thousand rolls of film. In one of the boxes, he eventually found an envelope with the name Vivian Maier scrawled on it. He googled her name and found a Chicago Tribune obituary. She had died a few days earlier. She was 83.

It's impossible to take stock of Vivian Maier's photos without taking stock of her story. She was by all accounts remarkably private, someone who didn't always enjoy the company of other adults. And yet her photographs feel like a celebration of people—a celebration of what Studs Terkel, the late grand oral historian, liked to call "the etceteras" of the world. (One photography scholar I spoke with suggested Terkel and Maier would have made a formidable pair, like James Agee and Walker Evans.)

Her subjects are often caught looking directly at the camera, apparently making eye contact with Maier, but she used a Rolleiflex, a box-shaped camera that requires the photographer to look downwards through the viewfinder. In other words, as it turns out, Maier didn't need to directly engage with her subjects, and many undoubtedly were unaware that she was, in fact, memorializing their images. Each feels like the beginning of a short story, a bit mysterious, not unlike Maier herself.